JP2019019686A - Diagnostic device for air-fuel ratio sensor of internal combustion engine - Google Patents

Abstract

To enable accurate diagnosis of the response characteristic of an air-fuel ratio sensor with respect to six deterioration modes of the OBD (On-Board Diagnostics) regulation.SOLUTION: Target air-fuel ratio change means 103 changes a target air-fuel ratio of feedback control to a rectangular wave shape. Response time constant detection means 104, 105 calculate a first time constant at the time when the target air-fuel ratio rises up on the basis of the output signal of an air-fuel ratio sensor 205, and a second time constant at the time when the target air-fuel ratio falls down, respectively. Dead time detection means 106, 107 calculate a first dead time at the time when the target air-fuel ratio rises up on the basis of the output signal, and a second dead time at the time when the target air-fuel ratio falls down, respectively. First to sixth response deterioration determination means 108-113 determine existence or nonexistence of response deterioration of the air-fuel ratio sensor 205 on the basis of at least one of the first and second time constants or at least one of the first and second dead times.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine.

  As a means for reducing harmful exhaust gas of automobiles and improving fuel economy and drivability, a feedback type air-fuel ratio control device that controls the air-fuel ratio by information on exhaust gas components of an internal combustion engine such as an engine has been put into practical use. ing.

  In the above air-fuel ratio control apparatus, abnormalities in exhaust gas components and abnormalities in the control system may occur when control cannot be performed properly due to failure or deterioration of the air-fuel ratio sensor itself used. In particular, the air-fuel ratio sensor described above is installed immediately after exhausting the engine, and therefore is susceptible to deterioration due to the influence of high temperature, high pressure, vibration, and bad fuel.

  In particular, automobiles for North America need to comply with OBDII regulations (laws that require the installation of on-board self-diagnosis devices), and if the air / fuel ratio sensor fails more than 1.5 times the exhaust emission control value. It is necessary to promptly warn the driver of the abnormality and prompt repair.

  Therefore, when the detection accuracy of the air-fuel ratio sensor decreases for some reason, it is necessary to take appropriate measures such as sensor replacement.

  The response characteristic of the air-fuel ratio sensor is that it is necessary to maintain a normal state in order to satisfactorily control the actual air-fuel ratio at the three-way point of the three-way catalyst by the air-fuel ratio feedback control. Is an essential technology in the OBDII regulations.

  Therefore, for the diagnosis of the response characteristic of the air-fuel ratio sensor, it is required by the OBDII regulation to detect six deterioration modes. A measure for detecting these six deterioration modes is required.

  Here, regarding the diagnosis of the response characteristic, a technique is known that can detect the response characteristic of the air-fuel ratio sensor by dividing it into a dead time and an n-th order lag characteristic (see, for example, Patent Document 1).

JP 2005-307961 A

  There are six deterioration modes shown in FIG. 4 for abnormal response characteristics of the air-fuel ratio sensor. This is a legal requirement for OBDII regulations and must be detected. Details of the six deterioration modes (1) to (6) are as follows.

(1) Rich → Lean response time error (2) Lean → Rich response time error (3) Rich → Lean / Lean → Rich both-side response time error (4) Rich → Lean dead time error (5) Lean → Rich dead time error (6) Rich → Lean / Lean → Rich both-side dead time abnormality There is a need for a means for accurately detecting these, but the technology disclosed in Patent Document 1 requires OBDII (On-Board Diagnostics II) regulation. It is not considered to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes.

  An object of the present invention is to provide an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine capable of accurately diagnosing the response characteristics of an air-fuel ratio sensor for six deterioration modes of OBD regulation.

  In order to achieve the above object, an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to the present invention includes a target air-fuel ratio changing unit that changes a target air-fuel ratio of feedback control into a rectangular waveform, and a target based on an output signal of the air-fuel ratio sensor. A first time constant calculating section for calculating a first time constant when the air-fuel ratio rises; and a second time constant for calculating a second time constant when the target air-fuel ratio falls based on an output signal of the air-fuel ratio sensor. 2 a time constant calculator, a first dead time calculator for calculating a first dead time when the target air-fuel ratio rises based on an output signal of the air-fuel ratio sensor, and an output signal of the air-fuel ratio sensor. A second dead time calculation unit for calculating a second dead time when the target air-fuel ratio falls based on at least one of the first time constant and the second time constant, or the second 1 dead time and the first Based on at least one of the dead time of the response deterioration determination unit determines the presence or absence of response deterioration of the air-fuel ratio sensor provided.

  According to the present invention, it is possible to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes of OBD regulation. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a block diagram of an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention. It is a figure which shows an example of the structure of the air-fuel ratio sensor diagnostic apparatus and internal combustion engine system by embodiment of this invention. It is a figure which shows the operation | movement of the existing LAF sensor response degradation diagnosis. It is a figure which shows six deterioration modes of a LAF sensor. It is a figure for demonstrating a temporary response degradation parameter | index and a response degradation parameter | index. It is a figure which shows the process of Formula (3) of FIG. This is the relationship between the response deterioration index and the time constant. It is a timing chart which detects the dead time of a LAF sensor. It is a flowchart (1) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (2) of the air fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (3) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (4) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (5) of the air fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (6) of the air fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (7) of the air fuel ratio sensor diagnostic apparatus by embodiment of this invention. It is a flowchart (8) of the air-fuel ratio sensor diagnostic apparatus by embodiment of this invention.

  Hereinafter, the configuration and operation of an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. The air-fuel ratio sensor diagnostic apparatus according to the present embodiment is a diagnostic apparatus for accurately diagnosing the above-described six deterioration modes in response deterioration diagnosis of an air-fuel ratio sensor attached to an internal combustion engine. In contrast, it is an essential technology.

  FIG. 1 shows a block diagram of an air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention. The air-fuel ratio is detected by the air-fuel ratio detection means of block 101. The diagnosis area is determined by the diagnosis area determination means in block 102. The diagnostic region determination unit determines whether or not the operation state such as the rotational speed of the internal combustion engine and the load of the internal combustion engine is within a predetermined range. The operation of the diagnostic area determination means will be described in detail with reference to FIG.

  The air / fuel ratio is changed to rich or lean by the target air / fuel ratio changing means in block 103. The time constant until the target lean air-fuel ratio is reached is detected by the rich-to-lean response time constant detecting means in block 104. The time constant until the target rich air-fuel ratio is reached is detected by the lean → rich response time constant detecting means of block 105. The dead time until the target lean air-fuel ratio is started is detected by the rich-to-lean dead time detection means in block 106. The lean → rich dead time detecting means in block 107 detects the dead time until the target rich air-fuel ratio is started.

  The air-fuel ratio sensor response deterioration determining means 1 in block 108 determines the rich → lean response abnormality by comparing the rich → lean response time constant with a predetermined value. The lean-to-rich response abnormality is determined by comparing the lean-to-rich response time constant with a predetermined value by the air-fuel ratio sensor response deterioration determining means 2 in block 109. By comparing the rich → lean response time and the lean → rich response time constant with predetermined values, the air / fuel ratio sensor response deterioration determining means 3 of block 110 determines rich → lean / lean → rich both-side response abnormality.

  The rich-to-lean dead time abnormality is determined by comparing the rich-to-lean dead time with a predetermined value by the air-fuel ratio sensor response deterioration determining means 4 in block 111. The air-fuel ratio sensor response deterioration determining means 5 of the block 112 compares the lean → rich wasted time with a predetermined value to determine lean → rich wasted time abnormality. By comparing the rich → lean dead time and lean → rich dead time with a predetermined value, the air / fuel ratio sensor response deterioration judging means 6 of block 113 judges rich → lean / lean → rich both-side dead time abnormality.

  The above is the outline of the embodiment of the present invention, and the internal combustion engine system that is the object of the embodiment of the present invention will be described below.

  FIG. 2 shows the configuration of an air-fuel ratio sensor diagnostic apparatus and an internal combustion engine system according to an embodiment of the present invention. The internal combustion engine system includes an internal combustion engine, an intake system, and an exhaust system, and an ignition device 201, a fuel injection device 202, and a rotation speed detection device 203 are attached to the internal combustion engine.

  The air flowing in from the air cleaner 200 is adjusted in flow rate by the throttle valve 213, then measured in flow rate by a flow rate detection device 204 (flow rate detection means), and fuel injected from the fuel injection device 202 at a predetermined angle. It is mixed and supplied to each cylinder 214. In addition, an air-fuel ratio sensor 205 such as an LAF sensor (Linear Air-Fuel ratio sensor) and a three-way catalyst 206 are attached to the exhaust system, and the exhaust gas is purified by the three-way catalyst 206 and is then released into the atmosphere. Discharged. The internal combustion engine controller 207 takes in the rotational speed Ne of the ring gear or the plate 208 by the output signal Qa of the flow rate detector 204 and the rotational speed detector 203 (the rotational speed detector), calculates the fuel injection amount Ti, and calculates the fuel injection amount Ti. Controls the injection amount of the injection device.

  Further, the internal combustion engine control device 207 detects the air-fuel ratio (A / F) in the internal combustion engine from the air-fuel ratio sensor 205 and corrects the fuel injection amount Ti so that the air-fuel ratio in the internal combustion engine becomes the stoichiometric air-fuel ratio. Air-fuel ratio feedback control is performed. Further, the air-fuel ratio after the catalyst is detected by the oxygen sensor 215.

  On the other hand, the fuel in the fuel tank 209 is sucked and pressurized by the fuel pump 210, and then led to the fuel inlet of the fuel injection device 202 through the fuel pipe 212 provided with the pressure regulator 211. Is returned to the fuel tank 209. The above is the target internal combustion engine system.

  2 includes a clock, a microcomputer (MPU: Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a timer / counter, an interface I / O, and an A / D conversion. Device, output circuit, digital input (port), analog input (port), etc.

  Next, the present invention will be specifically described. FIG. 3 shows the operation of the existing LAF sensor response deterioration diagnosis. In this diagnosis, the time after the diagnosis region is established is measured, and the number of rich lean inversions during that time is measured. If the counter value of the rich lean inversion count is equal to or greater than a determination value (NG determination value) after a predetermined determination time has elapsed after the diagnosis region is established, it is determined to be normal, and if it is less than the determination value, NG judge. In the case of FIG. 3, the operation at the normal time is shown.

  However, this method cannot determine the deterioration of the 6 modes shown in FIG. 4 in response to the OBDII regulation. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to an embodiment of the present invention aims to discriminate 6-mode degradation shown in FIG. 4 and detect an abnormality.

  First, a method for detecting response time delays (1), (2), and (3) shown in FIG. 4 will be described.

  FIG. 5 shows the principle. The target air-fuel ratio is changed from rich to lean and from lean to rich at predetermined time intervals. At this time, when formula (1) is established and arranged, the provisional response deterioration index IDXtmp is as follows.

  In Formula (1), since T> τ holds, Formula (2) holds.

  Therefore, it can be seen that the temporary response deterioration index IDXtmp is a parameter that is inversely proportional to the time constant τ of the response speed. Therefore, by taking the reciprocal of equation (2), it is possible to obtain a response deterioration index IDX proportional to the time constant τ (see equation (3)).

  Next, FIG. 6 will be described. FIG. 6 shows a process of the expression (3) described in FIG. The inverse of the final value obtained by differentiating, cutting the negative side, squaring and integrating becomes a response deterioration index proportional to the time constant τp at the time of rich → lean response. Note that A in FIG. 6 represents the final value obtained by integration.

  Further, the reciprocal of the final value obtained by differentiating, cutting off the positive side, squaring and integrating becomes a response deterioration index proportional to the time constant τm at the time of lean → rich response.

  Next, FIG. 7 will be described. FIG. 7 shows a temporary response deterioration index and a response deterioration index when the LAF sensor signal is actually subjected to response deterioration. The figure on the left is a provisional response deterioration index, and it can be seen that it is inversely proportional to the time constant. Thus, if the inverse is taken, it is possible to calculate a response deterioration index proportional to the time constant (see the right figure).

  When the rich → lean response deterioration index becomes larger than a predetermined NG threshold, it is determined that the rich → lean response is abnormal. Further, when the lean → rich response deterioration index becomes larger than a predetermined NG threshold, it is determined that the lean → rich response abnormality.

  Next, FIG. 8 will be described. FIG. 8 shows a method of detecting (4), (5), and (6) of the dead time delay shown in FIG. A state in which the LAF sensor signal does not change when the target air-fuel ratio changes from rich to lean is detected, or a state in which the LAF sensor signal does not change further when the target air-fuel ratio changes from lean to rich.

  The rich-to-lean dead time timer Dp is incremented from the time when the target air-fuel ratio changes from rich to lean, and the time until it exceeds a predetermined value αp is measured. When this is integrated every predetermined period and exceeds a predetermined threshold, it is determined that the rich → lean dead time abnormality. Further, the lean-to-rich dead time timer Dm is incremented from the time when the target air-fuel ratio changes from lean to rich, and the time until the target air-fuel ratio falls below the predetermined value αm is measured. When this is integrated for every predetermined period and exceeds a predetermined threshold value, it is determined that lean → rich wasted time abnormality.

  Hereinafter, the flowchart of the present invention will be described.

  FIG. 9 shows a flowchart of the present embodiment. FIG. 9 is a flowchart of diagnosis area determination.

  In step 901, it is checked whether the rotational speed of the internal combustion engine is within a predetermined range. In step 902, it is checked whether the load of the internal combustion engine is within a predetermined range. In step 903, it is checked whether the water temperature is within a predetermined range. In step 904, it is checked whether the vehicle speed is within a predetermined range. In step 905, it is checked whether the intake air temperature is within a predetermined range.

  In step 906, it is checked whether the atmospheric pressure is equal to or higher than a predetermined value. In step 907, it is checked whether the battery voltage is within a predetermined range. In step 908, it is checked whether the fuel is being cut. In step 909, it is checked whether air-fuel ratio control feedback is being performed. In step 910, the sensor used is checked for failure.

  If all the conditions of Steps 901 to 910 are satisfied in Step 911, it is determined that it is in the diagnosis region. If even one is off, it is determined in step 912 that it is outside the diagnostic area.

  Next, the flowchart of FIG. 10 will be described. FIG. 10 shows processing for storing the LAF sensor signal in the RAM of the microcomputer. Here, the LAF sensor signal is input every 10 ms. For example, the MPU of the internal combustion engine controller 207 stores the air / fuel ratio (A / F) indicated by the LAF sensor signal in the RAM as a variable LAF. In this embodiment, an example in which a 10 ms task is used is shown, but this is not a limitation.

  Next, the flowchart of FIG. 11 will be described. FIG. 11 is a flowchart for detecting rich → lean response deterioration (detection of (1) in FIG. 4).

  In step 1101, it is determined whether a diagnostic area is established. If it is not the diagnostic region, the square value integrated value Ip is cleared in step 1102. If it is a diagnostic region, the process proceeds to step 1103 and subsequent steps, and the difference value of LAF is calculated in step 1103. If the difference value of the LAF shows a negative value in step 1104, a process of setting it to zero is executed. In step 1105, the square value is calculated.

  In step 1106, the square value is added to the square value integrated value Ip. If N reaches a predetermined period in step 1107, the process proceeds to step 1108. If N does not reach a predetermined period, the process is terminated without executing the subsequent processes (N is calculated in FIG. 14). In step 1108, a predetermined value is divided by Ip, and a diagnostic index τp proportional to the time constant is calculated. If it is determined in step 1109 that τp is larger than the NG threshold, it is determined as abnormal in step 1110, and if it is less than that, it is determined normal in step 1111.

  In other words, the MPU of the internal combustion engine control device 207 determines the time constant (first time) when the target air-fuel ratio rises (rich → lean) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as rich → lean response time constant detecting means 104 (first time constant calculation unit) for calculating (time constant). In the present embodiment, the diagnostic index τp proportional to the time constant is calculated. However, τp when the proportionality constant is 1 is the time constant when the target air-fuel ratio rises (rich → lean).

  Specifically, the rich-to-lean response time constant detection means 104 (first time constant calculation unit) differentiates the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor) and cuts zero or less, The time constant (first time constant) when the target air-fuel ratio rises (rich → lean) is calculated by squaring, integrating, and taking the reciprocal.

  Since the time constant is approximated by a first-order lag, the logic becomes simple. Therefore, calculation can be performed at high speed.

  Next, the flowchart of FIG. 12 will be described. FIG. 12 is a flowchart for detecting lean → rich response deterioration (detection (2) in FIG. 4).

  In step 1201, it is determined whether a diagnostic area is established. If it is not the diagnosis region, the square value integrated value Im is cleared in step 1202. If it is a diagnosis region, the process proceeds to steps after step 1203, and the difference value of LAF is calculated in step 1203. If the difference value of the LAF shows a positive value in step 1204, a process of setting it to zero is executed. In step 1205, the square value is calculated.

  In step 1206, the square value is added to the square value integrated value Im. If N reaches a predetermined period in step 1207, the process proceeds to step 1208. If N does not reach the predetermined period, the process is terminated without executing the subsequent processes (N is calculated in FIG. 14). In step 1208, a predetermined value is divided by Im, and a diagnostic index τm proportional to the time constant is calculated. In step 1209, if the τm is larger than the NG threshold, it is determined as abnormal in step 1210, and if it is below, it is determined as normal in step 1211.

  In other words, the MPU of the internal combustion engine control device 207 determines the time constant (second) when the target air-fuel ratio falls (lean to rich) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). Function as a lean → rich response time constant detection means 105 (second time constant calculation unit). In this embodiment, the diagnostic index τm proportional to the time constant is calculated. However, τm when the proportionality constant is 1 is the time constant itself when the target air-fuel ratio falls (lean to rich). .

  Specifically, the lean → rich response time constant detection means 105 (second time constant calculation unit) differentiates the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor), cuts zero or more, The time constant (second time constant) when the target air-fuel ratio falls (lean to rich) is calculated by squaring, integrating, and taking the reciprocal.

  The detection of (3) in FIG. 4 is determined to be abnormal when an abnormality is determined at step 1110 in FIG. 11 and an abnormality is determined at step 1210 in FIG.

  Next, the flowchart of FIG. 13 will be described. FIG. 13 is a flowchart of control for changing the target air-fuel ratio every predetermined time.

  In step 1301, it is determined whether a diagnostic area is established. If it is not in the diagnosis region, the target air-fuel ratio is normally calculated in step 1303 by air-fuel ratio feedback control. If it is in the diagnosis region, the process proceeds to step 1302 and the subsequent steps. In step 1302, the target air-fuel ratio is set to a lean value. In step 1304, it is checked whether the timer Ta has reached a predetermined time. If not, in step 1306, 10 ms is added to the Ta. If so, the target air-fuel ratio is set to a rich value in step 1305. Next, in step 1307, it is checked whether the timer Tb has reached a predetermined time. If not, in step 1308, 10 ms is added to Tb. If it has reached, in step 1309, the Ta and Tb are cleared to zero.

  In other words, the MPU of the internal combustion engine control device 207 functions as target air-fuel ratio changing means 103 (target air-fuel ratio changing unit) that changes the target air-fuel ratio of feedback control into a rectangular wave shape.

  Next, the flowchart of FIG. 14 will be described. FIG. 14 is a flowchart for calculating N. N is a variable that is incremented every time the target air-fuel ratio changes by one cycle. In step 1401, it is determined whether a diagnosis area is established. If it is not a diagnostic region, N is cleared to zero in step 1404. If it is in the diagnosis region, the rising edge of the target air-fuel ratio is checked in step 1402. If it is a rising edge, increment N. If it is not a rising edge, N is not processed.

  Next, the flowchart of FIG. 15 will be described. FIG. 15 is a flowchart for detecting rich → lean dead time deterioration (detection of (4) in FIG. 4).

  First, in step 1501, it is determined whether a diagnosis area is established. If it is the diagnosis area, it is checked in step 1502 whether the flag Rp is 1. If it is not the diagnostic region, the flag Rp is set to zero in step 1508. If the flag Rp is zero in step 1502, the rising edge of the target air-fuel ratio is checked in step 1505. If it is established, the flag Rp is set to 1 in step 1506.

  Returning to step 1502, if the flag Rp is 1, then in step 1503 the LAF is compared with the rich value + αp value (threshold value for determining dead time). As a result of the comparison, if LAF is small, it is determined that it is in a dead time state, and in step 1504, 10 ms is added to the dead time timer Dp.

  Next, the falling edge of the target air-fuel ratio is checked at step 1507, and if it is established, Rp is set to zero at step 1508. If not, it is checked in step 1509 whether N has reached a predetermined period. If it has reached, a dead time timer Dp is compared with an NG threshold value in step 1510. If the dead time timer Dp is larger than the NG threshold value as a result of the comparison, it is determined in step 1511 that there is an abnormality. If it is equal to or less than the NG threshold, it is determined as normal in step 1512.

  In other words, the MPU of the internal combustion engine control device 207 uses the dead time (first time) when the target air-fuel ratio rises (rich → lean) based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as rich → lean dead time detection means 106 (first dead time calculation unit) for calculating (dead time). In this embodiment, the total sum (integrated value) of the dead time when the target air-fuel ratio rises (rich → lean) in a predetermined period N is calculated, but the total dead time when N = 1 is This is the dead time when the target air-fuel ratio rises (from rich to lean).

  Specifically, the rich → lean dead time detection means 106 (first dead time calculation unit) starts from the rise of the target air-fuel ratio until the air-fuel ratio becomes the sum of the rich value and the αp value (first threshold). Is measured as a dead time (first dead time). Specifically, the rich → lean dead time detecting means 106 (first dead time calculation unit) calculates the sum of dead times (first dead time) in a predetermined period N. Thereby, even if the dead time as noise enters the sum, the influence can be suppressed.

  Next, the flowchart of FIG. 16 will be described. FIG. 16 is a flowchart for detecting lean → rich dead time deterioration (detection (5) in FIG. 4).

  First, in step 1601, it is determined whether a diagnostic area is established. If it is the diagnosis area, it is checked in step 1602 whether the flag Rm is 1. If it is not the diagnostic region, the flag Rm is set to zero in step 1608. If the flag Rm is zero in step 1602, the falling edge of the target air-fuel ratio is checked in step 1605. If it is satisfied, the flag Rm is set to 1 in step 1606.

  Returning to step 1602, if the flag Rm is 1, the LAF is compared with the lean value−αm value (threshold value for determining the dead time) in step 1603. As a result of the comparison, if LAF is small, it is determined that there is a dead time state, and in step 1604, 10 ms is added to the dead time timer Dm.

  Next, the rising edge of the target air-fuel ratio is checked at step 1607, and if it is established, Rm is set to zero at step 1608. If not, it is checked in step 1609 whether N has reached a predetermined period. If it has reached, the dead time timer Dm is compared with an NG threshold value in step 1610. If the dead time timer Dm is larger than the NG threshold value as a result of the comparison, it is determined in step 1611 that there is an abnormality. If it is equal to or less than the NG threshold, it is determined as normal in step 1612.

  The detection of (6) in FIG. 4 is determined to be abnormal when an abnormality is determined in step 1511 in FIG. 15 and an abnormality is determined in step 1611 in FIG.

  In other words, the MPU of the internal combustion engine control device 207 determines the dead time (second dead time) when the target air-fuel ratio falls based on the output signal (LAF sensor signal) of the air-fuel ratio sensor 205 (LAF sensor). It functions as lean to rich dead time detection means 107 (second dead time calculation unit) to calculate. In this embodiment, the sum of the dead time when the target air-fuel ratio falls (lean → rich) in a predetermined period N is calculated, but the sum of the dead time when N = 1 is calculated as the target air-fuel ratio. Is the dead time itself when falling (lean → rich).

  Specifically, the lean → rich dead time detection means 107 (second dead time calculation unit) sets the air / fuel ratio to the sum of the lean value and the −αp value (second threshold) after the target air / fuel ratio falls. The time until this is measured as a dead time (second dead time). Specifically, the lean → rich wasted time detection unit 107 (second wasted time calculation unit) calculates the sum of the wasted time (second wasted time) in a predetermined period N.

  The MPU of the internal combustion engine control device 207 has a time constant (first time constant) when the target air-fuel ratio rises (rich → lean) and a time constant (first time constant) when the target air-fuel ratio falls (lean → rich). 2 or a dead time when the target air-fuel ratio rises (rich → lean) (first wasted time) and a dead time when the target air-fuel ratio falls (second wasted time). Based on at least one of (time), a response deterioration determining unit (air-fuel ratio sensor response deterioration determining means 1 (108) to air-fuel ratio sensor response deterioration determining means 6 ( 113)).

  This makes it possible to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes of OBD regulation.

  Specifically, the air-fuel ratio sensor response deterioration determination means 1 (108) as the first response deterioration determination unit is based on the time constant (first time constant) when the target air-fuel ratio rises (rich to lean). Then, the presence / absence of response deterioration (first response deterioration) of the air-fuel ratio sensor 205 is determined. Specifically, the air-fuel ratio sensor response deterioration determining means 1 (108) determines that the time constant (first time constant) when the target air-fuel ratio rises (rich → lean) is greater than the threshold (third threshold). The air-fuel ratio sensor 205 is determined to have a response deterioration (first response deterioration).

  Thereby, it is possible to accurately detect the response deterioration of the air-fuel ratio sensor 205 from the time constant (response time delay) when the target air-fuel ratio rises (rich → lean).

  The air-fuel ratio sensor response deterioration determination means 2 (109) as the second response deterioration determination unit is based on the time constant (second time constant) when the target air-fuel ratio falls (lean → rich). The presence / absence of the 205 response deterioration (second response deterioration) is determined. Specifically, the air-fuel ratio sensor response deterioration determining means 2 (109) has a time constant (second time constant) when the target air-fuel ratio falls (lean → rich) larger than a threshold value (fourth threshold value). In this case, the air-fuel ratio sensor 205 is determined to have a response deterioration (second response deterioration).

  Thereby, it is possible to accurately detect the response deterioration of the air-fuel ratio sensor 205 from the time constant (response time delay) when the target air-fuel ratio falls (from lean to rich).

  The air-fuel ratio sensor response deterioration determination means 3 (110) as the third response deterioration determination unit decreases the time constant (first time constant) and the target air-fuel ratio when the target air-fuel ratio rises (rich → lean). The presence or absence of response deterioration (third response deterioration) of the air-fuel ratio sensor 205 is determined based on the time constant (second time constant) at the time of (lean → rich). Specifically, the air-fuel ratio sensor response deterioration determining means 3 (110) has a time constant (first time constant) when the target air-fuel ratio rises (rich → lean) greater than a threshold (third threshold), In addition, when the time constant (second time constant) when the target air-fuel ratio falls (lean to rich) is larger than the threshold value (fourth threshold value), the response deterioration of the air-fuel ratio sensor 205 (third response deterioration) It is determined that there is.

  As a result, it is possible to accurately detect the response deterioration of the air-fuel ratio sensor 205 from the time constant (response time delay) when the target air-fuel ratio rises (rich → lean) and the time constant when the target air-fuel ratio falls (lean → rich). can do.

  The air-fuel ratio sensor response deterioration determination means 4 (111) as the fourth response deterioration determination unit is based on the dead time (first dead time) when the target air-fuel ratio rises (rich → lean). The presence or absence of the response deterioration (fourth response deterioration) is determined. Specifically, in the air-fuel ratio sensor response deterioration determination means 4 (111), the sum of the dead time (first dead time) when the target air-fuel ratio rises (rich → lean) is greater than the threshold (fifth threshold). If larger, it is determined that there is a response deterioration (fourth response deterioration) of the air-fuel ratio sensor 205.

  Thereby, it is possible to accurately detect the response deterioration of the air-fuel ratio sensor 205 from the dead time (dead time delay) when the target air-fuel ratio rises (rich → lean).

  The air-fuel ratio sensor response deterioration determination means 5 (112) as the fifth response deterioration determination unit is based on the dead time (second dead time) when the target air-fuel ratio falls (second dead time). The presence / absence of fifth response deterioration) is determined. Specifically, the air-fuel ratio sensor response deterioration determining means 5 (112) determines that the empty time (second waste time) when the target air-fuel ratio falls is greater than the threshold value (sixth threshold value). It is determined that there is response deterioration (fifth response deterioration) of the fuel ratio sensor 205.

  Thereby, it is possible to accurately detect the response deterioration of the air-fuel ratio sensor 205 from the dead time (dead time delay) when the target air-fuel ratio falls (from lean to rich).

  The air-fuel ratio sensor response deterioration determining means 6 (113) as the sixth response deterioration determining unit decreases the dead time (first dead time) and the target air-fuel ratio when the target air-fuel ratio rises (rich → lean). The presence / absence of response deterioration (sixth response deterioration) of the air-fuel ratio sensor 205 is determined based on the dead time (second dead time). Specifically, in the air-fuel ratio sensor response deterioration determining means 6 (113), the sum of dead time (first dead time) when the target air-fuel ratio rises (rich → lean) is greater than a threshold (fifth threshold). If the sum of the dead time (second dead time) when the target air-fuel ratio falls is larger than the threshold (sixth threshold), the response deterioration (sixth response deterioration) of the air-fuel ratio sensor 205 is caused. It is determined that there is.

  Accordingly, the response of the air-fuel ratio sensor 205 from the dead time (dead time delay) when the target air-fuel ratio rises (rich → lean) and the dead time (dead time delay) when the target air-fuel ratio falls (lean → rich). Degradation can be accurately detected.

  As described above, according to the present embodiment, it is possible to accurately diagnose the response characteristics of the air-fuel ratio sensor for the six deterioration modes of the OBD regulation.

  In addition, you may implement | achieve part or all of each said structure, a function (means), etc. with hardware, for example by designing with an integrated circuit. Each of the above-described configurations, functions (means), and the like may be realized by software by interpreting and executing a program that realizes each function by the processor (MPU). Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  When the MPU of the internal combustion engine control device 207 detects response deterioration of the six deterioration mode air-fuel ratio sensors of the air-fuel ratio sensor, a warning lamp or the like may be turned on to notify the driver of the warning. For example, six lamps for notifying the first to sixth response deteriorations may be provided, or one lamp may be provided, and the lighting state (color, blinking) depending on the combination of the presence or absence of the first to sixth response deteriorations ) May be changed.

  Moreover, the following aspects may be sufficient as embodiment of this invention.

  (11) An air-fuel ratio correction coefficient is calculated based on a catalyst provided in the exhaust system of the internal combustion engine and a signal from the pre-catalyst air-fuel ratio sensor for detecting a specific component concentration in the exhaust gas, and a reference fuel In a control apparatus for an internal combustion engine having an air-fuel ratio feedback control means for correcting a supply amount, a target air-fuel ratio changing means, a means for detecting a rich-to-lean response time constant of the pre-catalyst air-fuel ratio sensor, Means for detecting the lean-to-rich response time constant of the fuel ratio sensor, means for detecting the rich-to-lean dead time of the pre-catalyst air-fuel ratio sensor, and detecting the lean-to-rich dead time of the pre-catalyst air-fuel ratio sensor Means for detecting a diagnosis area, a response time constant detection means for detecting a response deterioration of the air-fuel ratio sensor based on the results of the response time constant detection means and the dead time detection means. Air-fuel ratio sensor diagnostic apparatus for an internal combustion engine and having a means.

  (12) The target air-fuel ratio changing means is characterized in that when a predetermined time elapses after the change from rich to lean, the change from lean to rich is repeated, and when the predetermined time elapses, the change from rich to lean is repeated again. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11).

  (13) The means for detecting the rich-to-lean response time constant of the pre-catalyst air-fuel ratio sensor differentiates the pre-catalyst air-fuel ratio sensor signal while executing the target air-fuel ratio changing means, and cuts below zero. 2. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), wherein the integration is performed after squaring and the rich to lean response time constant is detected from the inverse thereof.

  (14) The means for detecting the lean to rich response time constant of the pre-catalyst air-fuel ratio sensor differentiates the pre-catalyst air-fuel ratio sensor signal while executing the target air-fuel ratio changing means, and cuts zero or more. 2. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), wherein the air-fuel ratio sensor diagnostic apparatus for internal combustion engine according to (11), which is integrated after squaring and detects a lean → rich response time constant from the inverse thereof.

  (15) The means for detecting the rich-to-lean dead time of the pre-catalyst air-fuel ratio sensor is the time until the predetermined air-fuel ratio changing means is reached while starting the target air-fuel ratio changing means. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), which measures and detects a rich → lean dead time.

  (16) The means for detecting the lean-to-rich dead time of the pre-catalyst air-fuel ratio sensor is the time until the predetermined air-fuel ratio change means is reached while the target air-fuel ratio change means is being executed. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), which measures and detects a lean → rich dead time.

  (17) The diagnostic region determination means includes a rotation speed within a predetermined range, an engine load within a predetermined range, a water temperature within a predetermined range, a vehicle speed within a predetermined range, an intake air temperature within a predetermined range, and an atmospheric pressure greater than or equal to a predetermined value, The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (11), characterized in that a diagnosis region is set when the battery voltage is within a predetermined range, the fuel is not cut, the air-fuel ratio feedback is in progress, and the sensor used does not fail. .

  (18) The internal combustion engine according to (13), wherein the air-fuel ratio sensor response deterioration determining means determines that the rich → lean response is abnormal when the response time constant of (13) is longer than an NG threshold. Air-fuel ratio sensor diagnostic device.

  (19) The air-fuel ratio sensor response deterioration determining means determines that the lean → rich response is abnormal when the response time of (14) is longer than the NG threshold value. Fuel ratio sensor diagnostic device.

  (20) The air-fuel ratio sensor response deterioration determining means determines that the rich → lean / lean → rich both-side response is abnormal when the response times of (13) and (14) are both longer than the NG threshold. The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (13) or (14).

  (21) The internal combustion engine according to (15), wherein the air-fuel ratio sensor response deterioration determining means determines that the rich → lean dead time is abnormal when the dead time of (15) is longer than an NG threshold. Air-fuel ratio sensor diagnostic device.

  (22) The internal combustion engine according to (16), wherein the air-fuel ratio sensor response deterioration determining means determines that the lean → rich waste time is abnormal when the waste time in (16) is longer than an NG threshold. Air-fuel ratio sensor diagnostic device.

  (23) The air-fuel ratio sensor response deterioration determining means determines that the rich → lean / lean → rich both-side dead time is abnormal when the dead time of (15) and (16) is longer than the NG threshold. (15) The air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to (16).

  For example, the target air-fuel ratio is swung from rich to lean or from lean to rich, and at that time, the air-fuel ratio sensor signal is differentiated, squared and integrated, and the response time constant is detected from the reciprocal thereof. When rich or lean, the time until reaching a predetermined value is measured from that point. By doing so, the six deterioration modes shown in FIG. 4 can be accurately diagnosed.

101: Air-fuel ratio detecting means 102: Diagnosis region determining means 103: Target air-fuel ratio changing means 104: Rich → lean response time constant detecting means 105: Lean → rich response time constant detecting means 106: Rich → lean dead time detecting means 107: Lean → rich dead time detecting means 108: air-fuel ratio sensor response deterioration determining means 1
109: Air-fuel ratio sensor response deterioration judging means 2
110: Air-fuel ratio sensor response deterioration determining means 3
111: Air-fuel ratio sensor response deterioration determining means 4
112: Air-fuel ratio sensor response deterioration determining means 5
113: Air-fuel ratio sensor response deterioration judging means 6
200: Air cleaner 201: Ignition device 202: Fuel injection device 203: Revolution detection device 204: Flow rate detection device 205: Pre-catalyst oxygen sensor 206: Catalyst 207: Internal combustion engine control device 208: Plate or ring gear 209: Fuel tank 210 : Fuel pump 211: Pressure regulator 212: Fuel pipe 213: Throttle valve 214: Cylinder 215: Oxygen sensor after catalyst

Claims (7)

A target air-fuel ratio changing unit that changes the target air-fuel ratio of the feedback control into a rectangular waveform;
A first time constant calculating unit for calculating a first time constant when the target air-fuel ratio rises based on an output signal of the air-fuel ratio sensor;
A second time constant calculation unit for calculating a second time constant when the target air-fuel ratio falls based on an output signal of the air-fuel ratio sensor;
A first dead time calculation unit for calculating a first dead time when the target air-fuel ratio rises based on an output signal of the air-fuel ratio sensor;
A second dead time calculation unit for calculating a second dead time when the target air / fuel ratio falls based on an output signal of the air / fuel ratio sensor;
The response of the air-fuel ratio sensor based on at least one of the first time constant and the second time constant, or at least one of the first dead time and the second dead time. A response deterioration determination unit that determines presence or absence of deterioration;
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, comprising: An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The response deterioration determination unit
A first response deterioration determination unit that determines the presence or absence of the first response deterioration of the air-fuel ratio sensor based on the first time constant;
A second response deterioration determination unit that determines presence or absence of second response deterioration of the air-fuel ratio sensor based on the second time constant;
A third response deterioration determining unit that determines presence or absence of a third response deterioration of the air-fuel ratio sensor based on the first time constant and the second time constant;
A fourth response deterioration determining unit that determines presence or absence of a fourth response deterioration of the air-fuel ratio sensor based on the first dead time;
A fifth response deterioration determination unit that determines presence or absence of a fifth response deterioration of the air-fuel ratio sensor based on the second dead time;
An internal combustion engine comprising: a sixth response deterioration determining unit that determines whether or not the air-fuel ratio sensor has a sixth response deterioration based on the first dead time and the second dead time. Engine air-fuel ratio sensor diagnostic device. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The first time constant calculator is
The first time constant is calculated by differentiating the output signal of the air-fuel ratio sensor, cutting zero or less, squaring, integrating, and taking the reciprocal. Fuel ratio sensor diagnostic device. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The second time constant calculator is
The second time constant is calculated by differentiating the output signal of the air-fuel ratio sensor, cutting zero or more, squaring, integrating, and taking the reciprocal. Fuel ratio sensor diagnostic device. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The first dead time calculation unit is:
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, wherein a time from when the target air-fuel ratio rises until the air-fuel ratio reaches a first threshold is measured as the first dead time. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 1,
The second dead time calculator is
An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine, wherein a time from when the target air-fuel ratio falls until the air-fuel ratio reaches a second threshold is measured as the second dead time. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine according to claim 2,
The first time constant calculator is
The first time constant is calculated by differentiating the output signal of the air-fuel ratio sensor, cutting zero or less, squaring, integrating, and taking the reciprocal,
The second time constant calculator is
The second time constant is calculated by differentiating the output signal of the air-fuel ratio sensor, cutting zero or more, squaring, integrating, and taking the reciprocal,
The first dead time calculation unit is:
The time from when the target air-fuel ratio rises to the time when the air-fuel ratio becomes the first threshold is measured as the first dead time, and the sum of the first dead times in a predetermined period is calculated.
The second dead time calculator is
A time from when the target air-fuel ratio falls until the air-fuel ratio reaches the second threshold is measured as the second dead time, and the sum of the second dead times in a predetermined period is calculated;
The first response deterioration determination unit is
If the first time constant is greater than a third threshold, it is determined that there is a first response deterioration of the air-fuel ratio sensor;
The second response deterioration determining unit is
If the second time constant is greater than a fourth threshold, it is determined that there is a second response deterioration of the air-fuel ratio sensor;
The third response deterioration determination unit is
If the first time constant is greater than a third threshold value and the second time constant is greater than a fourth threshold value, it is determined that there is a third response deterioration of the air-fuel ratio sensor;
The fourth response deterioration determination unit is
If the sum of the first dead times is greater than a fifth threshold, it is determined that there is a fourth response deterioration of the air-fuel ratio sensor;
The fifth response deterioration determination unit
If the sum of the second dead times is greater than a sixth threshold, it is determined that there is a fifth response deterioration of the air-fuel ratio sensor;
The sixth response deterioration determination unit
When the sum of the first dead times is larger than a fifth threshold and the sum of the second dead times is larger than a sixth threshold, it is determined that there is a sixth response deterioration of the air-fuel ratio sensor. An air-fuel ratio sensor diagnostic apparatus for an internal combustion engine.

Images